从Cpanel通过SMTP发送邮件时出错

Question

我正尝试将邮件发送到gmail，因为我的主机服务是免费的，但是stacktrace说

com.sun.mail.util.MailConnectException: Couldn't connect to host, port: smtp.gmail.com, 587; 

虽然代码在我的Eclipse IDE上执行时工作正常。我问托管服务是否有任何防火墙可以阻止相同。但是他们否认了这一点，说你的ip在防火墙中没有被阻止，并且给定端口也在服务器上打开并且能够连接到远程服务器。那可能是问题的原因。这是代码

final String username = "xyz@gmail.com";
        final String password = "abcd";
        Properties properties = System.getProperties();
        properties.put("mail.smtp.auth", "true");
        properties.put("mail.smtp.starttls.enable", "true");
        properties.put("mail.smtp.host", "smtp.gmail.com");
        properties.put("mail.smtp.port", "587");
        Session session = Session.getInstance(properties,
                new javax.mail.Authenticator() {
                    protected javax.mail.PasswordAuthentication getPasswordAuthentication() {
                        return new javax.mail.PasswordAuthentication(username,
                                password);
                    }
                });
        out.print(session);
        response.setContentType("text/html");
        try {
            MimeMessage message = new MimeMessage(session);
            message.setFrom(new InternetAddress("xyz@gmail.com"));
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(
                    "abc@gmail.com"));
            message.setSubject("hello");
            message.setText("this is me");
            Transport.send(message);

        } catch (MessagingException mex) {
            out.print(mex);
        }

    }